Golf club

ABSTRACT

A set of golf club wedges each having a club face ( 10 ) is disclosed wherein the lofts of the individual clubs progressively increases. The hitting surface of each club head may take the form of an insert ( 12 ) that includes a series of grooves, the design of which is varied from club to club to provide increasing friction with loft. As a result, a golfer can impart the same amount of spin to a golf ball with each of the wedges despite a substantial difference in loft and club head swing speed between the respective clubs. In addition, the surface roughness of the hitting surface may also be increased as loft increases to further control the spin imparted to the ball.

This application claims priority under 35 U.S.C. § 371 based onInternational Application No. PCT/US02/36990, filed Nov. 18, 2002;published as WO 03/045507 on Jun. 5, 2003; which claims priority to U.S.Provisional Application Ser. No. 60/331,513, filed Nov. 19, 2001 andU.S. Provisional Application Ser. No. 60/351,623, filed Jan. 23, 2002.

This invention relates to golf clubs and, more particularly, to a set ofwedges having related physical characteristics enabling a golfer to moreaccurately control relatively short golf shots to a green.

BACKGROUND OF THE INVENTION

As golf clubs have evolved over the years, modern golfers often carrythree and sometimes four wedges to enhance the accuracy of golf shots toa green from about 120 yards or less. The distance a club is designedfor is dependent primarily on the loft angle of the club face. Forexample, a pitching wedge may have a loft of about 50 degrees and sandwedges a loft of about 56 degrees. Relatively recently, lofted wedgeshave become popular with lofts typically varying between 58 and 64degrees. Obviously, the distance for which a particular club is usedvaries significantly from golfer to golfer but for low handicap golfersthere is usually a significant difference in shot distance achieved whenusing a pitching wedge and a lofted wedge.

In addition to club loft, the flight of a golf ball is affected also bythe surface of the club which strikes the ball. It is known that thespin control of a ball is affected by the depth and placement of groovesin the face of the club as well as the friction characteristics of theclub face surface. Higher friction club face surfaces will impart morespin to a ball as will larger width grooves, sharper edged grooves,deeper grooves and more closely spaced grooves. The ability to impartbackspin to a golf ball tends to prevent the ball from moving in aforward direction after it lands on the green and therefore is usuallybeneficial, but excessive backspin can be detrimental in some cases. Forelite golfers, the ability to impart the same backspin to a ball for anyof a number of highly lofted clubs would be advantageous.

The principal object of this invention is to provide a series of wedgeswhich vary considerably in loft wherein the spin rate imparted to a golfball is approximately the same for each wedge, for a comparable swing.

SUMMARY OF THE INVENTION

In accordance with the invention, a series of wedges (for example, four)having different lofts is provided. The defining parameters of thegrooves of the individual clubs are progressively varied depending onloft, to provide increased friction with increased loft. By varying thegrooves in the faces as a function of club loft, a series of wedges isprovided in which the same spin rate can be achieved with each of theclubs in the series.

The wedges may utilize a club face of a constant surface roughness sothat, regardless of club loft, the surface friction is held constant andonly the grooves of each club are varied to provide the changing impactfriction required to provide constant spin rate. Alternatively, thefrictional characteristics of the striking face surfaces of the clubsmay also be controlled to provide progressively increasing surfacefriction from the lower lofted clubs to the higher lofted clubs.

In accordance with a further feature of the invention, the hittingsurface of the club is formed by an insert made of a material which willnot loose its frictional characteristics or groove shapes as rapidly asindustry common wedges with use. This is a problem with clubs havingsurfaces roughened by abrasive blasting. The insert enables the constantspin rate characteristic described above to be retained even afterpracticing sand shots over long periods of time.

THE DRAWINGS

FIG. 1 is a front elevational view showing the face of a wedge inaccordance with a preferred embodiment of the invention;

FIG. 2 is a bottom plan view of the wedge;

FIG. 3 is a side elevational view of the wedge;

FIG. 4 is a rear elevational view of the wedge; and

FIG. 5 comprises a series of schematic illustrations showing the grooveconfiguration for a series of four wedges in accordance with thepreferred embodiment of the invention.

DETAILED DESCRIPTION

As the loft of a wedge increases, the potential of the club to impartspin to the ball also increases. Spin also depends on how hard the ballis hit; all other things being equal, the harder the hit with a givenwedge, the greater the spin. In accordance with a preferred embodimentof the invention, the length of the shaft decreases and the weight ofthe head increases as the loft of the wedge increases. This means that aball will not be struck as hard with a higher lofted club (because itsshaft is shorter and head weight is greater, leading to slower swingspeeds from a constant effort by the golfer), with the result that thespin imparted to the ball is less. The invention takes intoconsideration the loft of the club and the hitting force for the club toprovide progressive changes in the club faces which will tend to produceconstant spin-induced reactions on a golf green, for each of a series ofwedges.

To compensate for the reduced spin imparted by the higher lofted clubs,in accordance with the invention the groove configuration is changed toincrease friction between the club face and the ball, to maintain spinresults as loft increases.

It is known that the characteristics of the grooves in the face of theclub affect the spin imparted to a golf ball. Generally speaking, thegreater the volume of the grooves, the greater the spin, especially outof wet or grassy lie conditions. USGA regulations prescribe in detailpermissible sizes and shapes of grooves as well as the spacing betweengrooves. In accordance with the invention, in order to impart the samespin to a golf ball for each of the various wedges in a set, certain ofthe defining parameters of the grooves are progressively changed fromwedge to wedge so that as loft increases and swing speeds decrease,greater spin per unit of club head speed is provided. The result ofthese changes (surface frictional characteristics and/or grooveparameters) is that a skilled golfer can impart approximately the samespin to a ball with any one of four wedges ranging from a 48° pitchingwedge to a 64° extra lofted wedge.

FIGS. 1–4 show an exemplary wedge in accordance with a preferredembodiment of the invention. The various parameters which define theclub are indicated in the drawings and in Table I below which lists thespecific design parameters for a set of four wedges in accordance with apreferred embodiment of the invention. The wedges are characterized as apitching wedge (P), sand wedge (S), lofted wedge (L), and an extralofted wedge (X). Obviously, the invention is not limited to specificdesign parameters and Table I is intended to be exemplary only.

The defining parameters of a groove are shape, width, depth, spacing andedge sharpness. See FIG. 5. The shape of the grooves is characterized as“V”, “U”, and “box”. A U-shaped groove has a slight curve at the bottomand a box-shaped groove is flat or approximately flat along its bottomsurface. The “30° rule” as illustrated in FIG. 5 defines the edges of agroove as the point of contact between each upper edge of the groove anda line drawn at 30° to the horizontal. Width is measured from edge toedge. In the preferred embodiment, shape and edge sharpness aredifferent in each case. As indicated in Table I, the top edge radiusdecreases as the loft of the wedge increases. This means that the higherlofted clubs have progressively sharper edges on the grooves whichaffects friction and spin control. The change in groove geometry (asloft increases) enables a skilled golfer to impart the same spin to aball with each of the wedges despite the differences in loft, shaftlength and club length.

In the preferred embodiment, the sole bounce dimensions (height anddepth) and flange width provide graduated contouring designed to provideoptimum turf glide for each wedge.

In the preferred embodiment of the invention, the club face 10 (FIG. 1)includes an insert 12 which is bonded to the face of the club. The widthand height of exemplary inserts are indicated in FIG. 1. The height ofan insert corresponds essentially to the entire face of the club betweenthe two lines representing the insert width. The insert is secured in asuitable recess within the club face in any suitable fashion, forexample, by an adhesive or by welding.

In the set of wedges defined in Table I, the roughness of the club facesurface is progressively increased as loft increases. In Table I,“surface roughness” refers to the difference between the average depthof the surface and the highest peak of the surface. The higher theindex, the greater the friction. “GC” means center of gravity. Thecombination of surface roughness and groove configuration enables closecontrol of the spin imparted to a ball, but it is not necessary that thesurface roughness vary from wedge to wedge. Excellent results have beenobtained where only the groove geometry of the club face insert isvaried to provide the constant spin rate. In this embodiment of theinvention, the surface roughness was maintained at approximately 180micro-inches for each of the club heads. The groove geometry conformedto Table I.

The preferred material for the club face insert is a high-strength 440Cstainless steel. This type of steel is manufactured and sold byCarpenter Technology Corporation under the trademark 440-XH™. Itschemical composition is approximately 1.60% carbon, 0.50% manganese,0.40% silicon, 16.00% chromium, 0.35% nickel, 0.80% molybdenum, 0.45%vanadium and the remaining amount iron. The steel composition ismicro-machined to the desired surface roughness (e.g. 180 microinches)and then tempered to the desired hardness, not to exceed 64 HRC(Rockwell Nominee Hardness). The insert may also be made of a highfriction powdered material comprising diamond, tungsten, carbide andbronze which was sintered to form an insert about 0.1 inches thick.

TABLE I Pitching Sand Lofted Extra-lofted Distance Control WedgeCategories P S L X Heads Material-forged CRS CRS CRS CRS Material-castSS-304 SS-304 SS-304 SS-304 Hardness, Soft Soft Soft Soft heat-treatmentFinish-forged Chrome plate Chrome Chrome Chrome plate plate plateFinish-cast Polished Polished Polished Polished Bounce Bounce-height 0.250  0.500  0.200  0.150 (inches) Bounce-depth  0.400  0.600  0.300 0.400 (inches) Sole flange width (inches at toe)  0.750  0.800  0.900 0.800 (inches at sweet  0.700  0.700  0.800  0.720 spot) (inches atheel)  0.550  0.500  0.550  0.500 Head weight (grams) 325 333 341 349Hosel length adjustable +/− .250 to  3.00  3.10  3.20  3.30 attainweight (inches) Weight cg: top-bottom  0.550  0.580  0.620  0.650distribution (inches) cg: heel-toe (inches)  0.920  0.940  0.960  0.980Grooves: top shape (overall) V U box box side angle (degrees  41  16  8 2 from vertical) top width (inches, 30  0.035  0.030  0.035  0.035degree rule) top edge radius (inches)  0.020  0.018  0.015  0.010spacing between edges  0.105  0.090  0.100  0.105 (inches) bottom shapeV U box box bottom radius (inches) r = .005 r = .012 r = .008 squaredepth (inches)  0.020  0.020  0.020  0.020 Surface 150 160 170 180roughness (micro inches) Loft (degrees)  49  55  60  64 Lie (degrees) 63  63.5  64  64.5

Most manufacturers tend to provide a constant shaft length for allwedges in a given set. In accordance with a preferred embodiment of theinvention, however, shaft length is decreased with increasing loft whichmeans that the distance provided by the club is diminished for thisreason as well. When a shaft is reduced in length, the natural(resonant) frequency of vibration increases, which causes the shaft tofeel stiffer. In the preferred embodiment of the invention, as the shaftlength is decreased with increasing loft, the frequency of the shaft(and thus its stiffness) is also decreased so that the “feel” of thevarious wedges remains unchanged.

Table II lists the defining parameters of exemplary shafts and gripswhich may be used with a set of wedges in accordance with the invention.

TABLE II Shafts Material: light weight steel Length: mens (inches) 35.535 34.5 34 ladies (inches) 34.5 34 33.5 33 Flex code letter (frequency)R (5.5) R (5.0) R (4.5) L (4.0) Off-set (inches)  0  0  0  0 GripsMaterial, color Rubber-black Rubber-black Rubber-black Rubber-blackShape-length (inches) round-11.5 round-11.5 round-11.5 round-11.5 Size:men top (diameter-inches)  1.10  1.10  1.10  1.10 bottom(diameter-inches)  0.95  0.95  0.95  0.95 ladies top (diameter-inches) 1.00  1.00  1.00  1.00 bottom (diameter-inches)  0.85  0.85  0.85  0.85

1. A set of at least three golf wedges having club heads ofprogressively increasing lofts, each of the club heads having a surfacefor striking a golf ball, with each surface including a series ofgrooves, the surfaces having frictional characteristics which increasewith club loft, wherein the frictional characteristics are controlled byvarying at least one of groove shape, groove spacing, groove edgesharpness, and surface roughness, the change in frictionalcharacteristics being selected so that the back spin imparted to a golfball when struck with equal force by each one of the wedges issubstantially the same.
 2. A set of wedges according to claim 1, whereineach of said wedges includes a shaft with the length and stiffness ofthe shafts decreasing with increasing loft.
 3. A set of wedges accordingto claim 1, wherein the shape of the grooves varies from wedge to wedge,with the sides of the grooves becoming progressively steeper withincreasing loft.
 4. A set of wedges according to claim 3, wherein theradii of the top edges of the grooves vary from wedge to wedge, with theradii of the top edges decreasing with increasing loft.
 5. A set ofwedges according to claim 3, wherein the surface roughness of saidsurfaces increases from wedge to wedge with increasing loft.
 6. A set ofwedges according to claim 1, wherein the radii of the top edges of thegrooves vary from wedge to wedge, with the radii of the top edgesdecreasing with increasing loft.
 7. A set of wedges according to claim6, wherein the surface roughness of said surfaces increases from wedgeto wedge with increasing loft.
 8. A set of wedges according to claim 1,wherein the surface roughness of said surfaces increases from wedge towedge with increasing loft.
 9. A set of wedges according to claim 1,wherein each of the said surfaces is provided in the form of an insertwhich is secured to the club head.
 10. A set of wedges according toclaim 1, wherein each of said wedges includes a shaft with the length ofthe shafts decreasing with increasing loft.
 11. A set of at least threegolf wedges having club heads of progressively increasing lofts, each ofthe club heads having a surface for striking a golf ball, with eachsurface including a series of grooves, the surfaces having frictionalcharacteristics which increase with club loft, wherein the frictionalcharacteristics are controlled by varying at least one of groove shape,groove spacing, and groove edge sharpness, the change in frictionalcharacteristics being selected so that the back spin imparted to a golfball when struck with equal force by each one of the wedges issubstantially the same.
 12. A set of wedges according to claim 11,wherein the shape of the grooves varies from wedge to wedge, with thesides of the grooves becoming progressively steeper with increasingloft.
 13. A set of wedges according to claim 12, wherein the surfaceroughness of said surfaces increases from wedge to wedge with increasingloft.
 14. A set of wedges according to claim 11, wherein the radii ofthe top edges of the grooves vary from wedge to wedge, with the radii ofthe top edges decreasing with increasing loft.
 15. A set of wedgesaccording to claim 14, wherein the surface roughness of said surfacesincreases from wedge to wedge with increasing loft.
 16. A set of wedgesaccording to claim 11–14, wherein the surface roughness of said surfacesincreases from wedge to wedge with increasing loft.
 17. A set of wedgesaccording to claim 11, wherein each of said wedges includes a shaft withthe length and stiffness of the shafts decreasing with increasing loft.18. A set of wedges according to claim 17, wherein the radii of the topedges of the grooves vary from wedge to wedge, with the radii of the topedges decreasing with increasing loft.